It has been proposed that idiopathic interstitial pneumonia (IIP) be divided into histopathologic categories. The overall prognosis differs between histopathologic categories; however, individual patients within categories can have an unpredictable response to therapy and survival. The potential for disease progression despite therapy often leads to the early listing of patients for lung transplantation as the mean time on the waiting list is 2-3 years. There is a shortage of donor lungs and this approach can lead to overpopulation of the waiting list and has the potential of preventing allocation of organs to the patients with the greatest need. This project will examine prognostic factors in patients with IIP and use these factors to develop a model that predicts survival. This model will help patients and physicians decide on optimal timing for lung transplantation. The histologic type of IIP is the most important, although not exclusive, factor influencing survival. Determination of histologic type requires a surgical biopsy which is not possible in all patients. Semi-quantitative high resolution CT (HRCT) scoring for the amount of fibrosis also gives prognostic information. A drawback of this technique is observer variability, which could limit widespread utilization. We will collaborate with the University of Iowa to utilize a computerized quantitative scoring system which quantifies HRCT patterns (ground glass, fibrosis) present in the lungs of patients with IIP. We hypothesize that a computerized technique to determine the baseline and serial change in the amount of fibrosis will provide key prognostic information for patients with IIP. It has been suggested that radiologists can accurately diagnose categories of IIP. We will utilize survival analyses to compare the impact of a histologic diagnosis compared to a HRCT diagnosis for patients with IIP. We hypothesize that radiologists will have moderate accuracy in the diagnosis of IIP and that a HRCT diagnosis will provide more prognostic information when compared to a surgically obtained histopathologic diagnosis. The change in a clinical, radiographic, and physiologic (CRP) scoring system after three months of treatment also influences prognosis. A drawback is the requirement of a cardiopulmonary exercise test. We hypothesize that a scoring system utilizing the change in oxygen saturation during a six-minute hall walk will provide equal information without the need for a cardiopulmonary exercise test. During the past 10 years patients undergoing CRP testing have also performed a six-minute walk test. This information will be utilized to develop a new exercise component for a modified CRP scoring system. We will utilize survival analysis to define the patient population most likely to have improved survival through lung transplantation.